Import coordinates from CSV and create sphere at each position
It has been a while since I have done any scripting, but the below should work based on your description. Note that the CSV file I made for testing included a header row, and the creation of objects for ease of testing was bpy.ops.mesh.primitive_uv_sphere_add()

bl_info = {
    "name": "Blank1",
    "author": "Your Name Here",
    "version": (1, 0),
    "blender": (2, 79, 0),
    "location": "View3D &gt; Tools panel 'T' &gt; Blank1 &gt; Blank2",
    "description": "",
    "warning": "",
    "wiki_url": "",
    "category": "",
    }

import bpy
import csv
from bpy.types import Operator
from bpy.types import Panel

class MeshGenTool():
    @classmethod
    def main(cls, context):
        scene = bpy.context.scene
        objs = importCSV(scene['CSVFile'])
        for obj in objs:
            bpy.ops.mesh.primitive_uv_sphere_add(size=obj[1], location=obj[0])
            MyMesh=bpy.context.object
            MyMesh.name = "MyMesh"

class MeshGenButton(bpy.types.Operator):
    """Execute generation"""
    bl_idname = "object.simple_operator"
    bl_label = "Generate"
    def execute(self, context):
        MeshGenTool.main(context)
        return {'FINISHED'}

# This is based on CSV file having a header row with the descriptions 'x', 'y', 'z', 'd'
def importCSV(CSVFile):
    obj_loc = ()
    obj_dia = 0
    obj_data = ()
    objs =[]
    with open(CSVFile) as csvfile:
        reader = csv.DictReader(csvfile)
        for row in reader:
            obj_loc = (float(row['x']), float(row['y']), float(row['z']))
            obj_dia = float(row['d'])
            obj_data = (obj_loc, obj_dia)
            objs.append(obj_data)
    return objs

class VIEW3D_PT_Blank1_Blank2(Panel):
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_category = "Blank1"
    bl_context = "objectmode"
    bl_label = "Blank2"

    def draw(self, context):
        layout = self.layout
        scene = bpy.context.scene
        row = layout.row()
        col = layout.column(align=True)
        scn = bpy.context.scene
        col.label(text="Blank2")
        col.prop(scene, "CSVFile")
        col.operator("object.simple_operator", text="Add items", icon='MESH_ICOSPHERE')

def register():
    bpy.utils.register_class(VIEW3D_PT_Blank1_Blank2)
    bpy.utils.register_class(MeshGenButton)
    bpy.types.Scene.CSVFile = bpy.props.StringProperty(
        name = "CSVFile",
        description = "Path of CSV File to read from",
        default = "",
        subtype = 'FILE_PATH')

def unregister():
    bpy.utils.unregister_class(VIEW3D_PT_Blank1_Blank2)
    bpy.utils.unregister_class(MeshGenButton)
    del bpy.types.Scene.CSVFile

if __name__ == "__main__":
    register()